Calling a woman a girl, while calling a man a man, might be why you find it hard to form positive rapport with her.
PS after giving this one more thought, i dont think i ever patronized someone because of gender, but must honestly admit i assume the mentor tone when dealing with unexperienced/less skilled developers. Shoot me, but it's not about maintaining my feeling of superiority, i know my skills. It's about building a rapport - if the other person reacts properly then there's hope for cooperation, if it's just games then sorry, i dont want that.
Do you habitually call any of the men you work with "boy"?
Maybe we should stop using the word 'girlfriend' and say 'womanfriend' instead?
And btw what about 'girls in tech' organization? Is it patronizing?
Boyfriend/girlfriend labels are equitable, and that relationship implies a familiarity for which a diminutive is typical and appropriate. Notably, this is not a professional relationship.
Girls in tech is about recruiting and supporting female children interested in tech. That's okay, because they're children. Your coworker is an adult, and it behooves you to treat them like one. For example, if she isn't acting like an adult, that's an issue to address in a professional manner, rather than call her a girl behind her back.
Ok i can swallow being accused of thoughtcrime (at least!), and will punish myself for it, but are you implying 'Girls in tech' is engaging in illegal employment of minors? That's a bold statement.